1. Field of the Invention
The present invention relates to a method and apparatus for predicting a higher-order components of high speed uniformity of a tire, in which a higher-order component (for example, a component of the second order or higher) of high speed uniformity at the time a tire rolls at a high speed is predicted based on low speed uniformity at the time the tire rolls at a low speed, and also relates to a method of manufacturing tires, which comprises the step of selecting a tire by using a higher-order component of high speed uniformity of the tire, which is predicted by the method or apparatus for predicting a higher-order component of high speed uniformity of a tire.
2. Description of the Related Art
The number of cases in which higher-order components of high speed uniformity of a tire cause noise due to vibration has recently increased. It is thought that this problem caused by the higher-order components of high speed uniformity has become marked due to a decrease in the value of the first-order component of tire uniformity.
Further, higher-order components of high speed uniformity cause a problem in the resonance phenomena with other tire characteristics (natural frequency, cavity resonance frequency, and the like), and depends on the natural frequency, the cavity resonance frequency, and the like, and also generates noise mainly comprised of booming noise, beat noise, or the like in the interior of a vehicle.
The uniformity of a tire results from various mechanisms depending on speed, and therefore, it cannot be said that the uniformity at the time of rolling at a low speed and the uniformity at the time of rolling at a high speed correspond to each other well. There have conventionally been known the following methods as methods for predicting higher-order components of high speed uniformity of a tire based on low speed uniformity.
(1) Method Using a Regression Equation
This is a method in which a high speed uniformity and a low speed uniformity are measured, and a regression equation is derived from the measured values and is used to make the high speed uniformity and the low speed uniformity correspond to each other.
(2) Method Using a Predictive Equation Based on Statistical Processing
In this method, several tens of tires prepared in advance are used, and a radial force variation (RFV) at a low speed, a radial force variation (RFV) at a high speed, and a rolling radius variation are measured. The first- through fourth-order components of a high speed tangential force variation (TFV) are predicted from a constant obtained by statistical processing from the above-described measured values, and from an RFV at a low speed and a rolling radius variation which are measured for each tire (see U.S. Pat. 5,396,438).
In both the above-described method using a regression equation and method using a predictive equation based on statistical processing, the low speed uniformity and the high speed uniformity are not strictly related to each other, and therefore, the low speed uniformity and the high speed uniformity do not correspond to each other well. Further, there is a drawback in that it is difficult to predict the high speed uniformity at an arbitrary speed and order.
Further, in the method using a predictive equation based on statistical processing, several tens of tires prepared in advance must be used for testing each at a low speed and at a high speed each time the contents of a lot are changed. Accordingly, there is a drawback in that much time is required.